docs: def bcr(eal_original, eal_retrofitted, interest_rate,
          asset_life_expectancy, asset_value, retrofitting_cost):
      """
      Compute the Benefit-Cost Ratio.
  
      BCR = (EALo - EALr)(1-exp(-r*t))/(r*C)
  
      Where:
  
      * BCR -- Benefit cost ratio
      * EALo -- Expected annual loss for original asset
      * EALr -- Expected annual loss for retrofitted asset
      * r -- Interest rate
      * t -- Life expectancy of the asset
      * C -- Retrofitting cost
      """
      return ((eal_original - eal_retrofitted) * asset_value *
              (1 - numpy.exp(- interest_rate * asset_life_expectancy)) /
              (interest_rate * retrofitting_cost))